GHSA-qh5x-rfwf-rvfv: Hysteria vulnerable to server crash when max_datagram_frame_size very small
An authenticated client can crash the Hysteria server by advertising a very small QUIC max_datagram_frame_size and triggering a UDP response. The server's fragmentation code does not handle cases where the UDP message header size exceeds the maximum datagram payload size, causing a slice bounds panic and server termination. This vulnerability affects Hysteria versions prior to 2.9.2.
AI Analysis
Technical Summary
The vulnerability exists in the Hysteria server's UDP response handling. When a client advertises a very small QUIC max_datagram_frame_size, the server attempts to send a UDP response via QUIC DATAGRAM but receives a DatagramTooLargeError. The server then tries to fragment the UDP message, but the fragmentation logic assumes the max datagram size is larger than the UDP message header. If this assumption is violated, a negative or zero payload size leads to a slice bounds panic, crashing the server process. This issue affects versions of github.com/apernet/hysteria before 2.9.2.
Potential Impact
An authenticated attacker can cause a denial of service by crashing the Hysteria server process. This results in server unavailability until restarted. There is no indication of confidentiality or integrity impact.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid accepting clients that advertise very small max_datagram_frame_size values. Monitor for updates from the Hysteria project regarding an official fix.
GHSA-qh5x-rfwf-rvfv: Hysteria vulnerable to server crash when max_datagram_frame_size very small
Description
An authenticated client can crash the Hysteria server by advertising a very small QUIC max_datagram_frame_size and triggering a UDP response. The server's fragmentation code does not handle cases where the UDP message header size exceeds the maximum datagram payload size, causing a slice bounds panic and server termination. This vulnerability affects Hysteria versions prior to 2.9.2.
CVSS v3.1
Affected software
Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability exists in the Hysteria server's UDP response handling. When a client advertises a very small QUIC max_datagram_frame_size, the server attempts to send a UDP response via QUIC DATAGRAM but receives a DatagramTooLargeError. The server then tries to fragment the UDP message, but the fragmentation logic assumes the max datagram size is larger than the UDP message header. If this assumption is violated, a negative or zero payload size leads to a slice bounds panic, crashing the server process. This issue affects versions of github.com/apernet/hysteria before 2.9.2.
Potential Impact
An authenticated attacker can cause a denial of service by crashing the Hysteria server process. This results in server unavailability until restarted. There is no indication of confidentiality or integrity impact.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid accepting clients that advertise very small max_datagram_frame_size values. Monitor for updates from the Hysteria project regarding an official fix.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-qh5x-rfwf-rvfv
- Osv Schema Version
- 1.4.0
- Aliases
- []
- Ecosystems
- ["Go"]
- Database Specific Severity
- HIGH
- Cvss Version
- 3.1
Threat ID: 6a3ef76e27e9c79719fee9d0
Added to database: 06/26/2026, 22:04:30 UTC
Last enriched: 06/26/2026, 22:09:35 UTC
Last updated: 06/26/2026, 22:09:35 UTC
Views: 2
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
External Links
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.